---
title: "Reference: handleChatStream() | AI SDK"
description: API reference for handleChatStream(), a framework-agnostic handler for streaming agent chat in AI SDK-compatible format.
---

import PropertiesTable from "@site/src/components/PropertiesTable";

# handleChatStream()

Framework-agnostic handler for streaming agent chat in AI SDK-compatible format. Use this function directly when you need to handle chat streaming outside Hono or Mastra's own [apiRoutes](/docs/v1/server-db/custom-api-routes) feature. 

`handleChatStream()` returns a `ReadableStream` that you can wrap with [`createUIMessageStreamResponse()`](https://ai-sdk.dev/docs/reference/ai-sdk-ui/create-ui-message-stream-response).

Use [`chatRoute()`](/reference/v1/ai-sdk/chat-route) if you want to create a chat route inside a Mastra server.

## Usage example

Next.js App Router example:

```typescript title="app/api/chat/route.ts" copy
import { handleChatStream } from '@mastra/ai-sdk';
import { createUIMessageStreamResponse } from 'ai';
import { mastra } from '@/src/mastra';

export async function POST(req: Request) {
  const params = await req.json();
  const stream = await handleChatStream({
    mastra,
    agentId: 'weatherAgent',
    params,
  });
  return createUIMessageStreamResponse({ stream });
}
```

## Parameters

<PropertiesTable
  content={[
    {
      name: "mastra",
      type: "Mastra",
      description: "The Mastra instance containing registered agents.",
      isOptional: false,
    },
    {
      name: "agentId",
      type: "string",
      description: "The ID of the agent to use for chat.",
      isOptional: false,
    },
    {
      name: "params",
      type: "ChatStreamHandlerParams",
      description: "Parameters for the chat stream, including messages and optional resume data.",
      isOptional: false,
    },
    {
      name: "params.messages",
      type: "UIMessage[]",
      description: "Array of messages in the conversation.",
      isOptional: false,
    },
    {
      name: "params.resumeData",
      type: "Record<string, any>",
      description: "Data for resuming a suspended agent execution. Requires `runId` to be set.",
      isOptional: true,
    },
    {
      name: "params.runId",
      type: "string",
      description: "The run ID. Required when `resumeData` is provided.",
      isOptional: true,
    },
    {
      name: "params.requestContext",
      type: "RequestContext",
      description: "Request context to pass to the agent execution.",
      isOptional: true,
    },
    {
      name: "defaultOptions",
      type: "AgentExecutionOptions",
      description: "Default options passed to agent execution. These are merged with params, with params taking precedence.",
      isOptional: true,
    },
    {
      name: "sendStart",
      type: "boolean",
      description: "Whether to send start events in the stream.",
      isOptional: true,
      defaultValue: "true",
    },
    {
      name: "sendFinish",
      type: "boolean",
      description: "Whether to send finish events in the stream.",
      isOptional: true,
      defaultValue: "true",
    },
    {
      name: "sendReasoning",
      type: "boolean",
      description: "Whether to include reasoning steps in the stream.",
      isOptional: true,
      defaultValue: "false",
    },
    {
      name: "sendSources",
      type: "boolean",
      description: "Whether to include source citations in the stream.",
      isOptional: true,
      defaultValue: "false",
    },
  ]}
/>